This invention relates to steering ball and socket joint assemblies for use in motor vehicles. More particularly, the invention relates to preloaded joint assemblies capable of maintaining relatively constant loading over their useful lives.
In designing a ball joint for use in steering linkage and suspension systems, an effort is typically made to provide a relatively constant rotating torque in the joint over its useful life. Normally a preload is applied to the joint during its manufacture to achieve an initial rotating torque value. However, over the useful life of the joint the torque value tends to decrease as result of wear, and wheel end lost motion and vibrations commensurately increase to the detriment of vehicular operation.
Attempts to overcome undesirable torque losses, hence to maintain given preload values, are legion. As one example, coil springs have bee positioned within ball socket cavities to continuously urge bearing members against balls during useful lives of Joint assemblies. However, as coil springs have relatively low compressive elastic moduli, the torques can rarely be set sufficiently high enough to meet desired values without exceeding size and space limits. Moreover, because the compressive load capacity of a coil spring varies with extension of the spring, a gradual reduction of bearing contact load, and hence rotating torque, occurs as direct result of dimensional changes due to wear.
Finally, prior art processes employed in the manufacture of prior art ball and socket joint assemblies have been inherently plagued with substantial deviations in initial preload, hence torque, values. Thus, ball joints have rarely been manufactured with satisfactory consistency in rotating torque values to begin with.